Comparative study on the use of cationic–nonionic-organo-montmorillonite in oil-based drilling fluids

Abstract This work involves a comparative study of cationic–nonionic-organo-montmorillonite (CNOMt), cationic-organo-montmorillonite (COMt) and nonionic-organo-montmorillonite (NOMt), aiming their use in oil-based drilling fluids. Firstly, CNOMt, COMt and NOMt were prepared in aqueous solution. Secondly, organo-montmorillonites were characterized by X-ray diffraction (XRD), differential thermal analysis (DTA), thermogravimetric analysis (TG), contact angle test, and swell index. The results indicated that cationic and nonionic surfactants could solely or synergistically intercalate into the interlayer spaces of montmorillonite. The order of their thermal stabilities was CNOMt > NOMt > COMt. The order of surface lipophilicity (or hydrophobicity) and swelling indices in oils was the same, i.e., CNOMt > COMt > NOMt. Finally, organo-montmorillonites were added into emulsions with different ratios of oil to water and their apparent viscosities were characterized. The results exhibited that both CNOMt and COMt viscosified the oil-based fluids better than NOMt did. In addition, the apparent viscosity of CNOMt was a little higher than that of COMt in the emulsion with oil/water ratio of 95:5 while the result was inverted in the emulsion with oil/water ratio of 80:20. From the standpoint of characterization results, CNOMt presented a new kind of potential rheological control additive of oil-based drilling fluids, especially for high oil/water ratio fluids, and CNOMt would perform excellent thermal stability.